The penetration of the skin by pharmacologically active agents contained in compositions for topical administration usually is slow and often too slow to be of practical value. The methods known in the art to enhance penetration frequently use adjuvants or mixtures of adjuvants to enhance absorption. However many of the more effective adjuvants irritate the skin or are toxic or smelly or stain the clothes they come into contact with.
Pentane-1,5-diol is known to possess antiviral, antifungal and antibacterial activity, in particular antiviral activity against herpes simples virus (U.S. Pat. No. 5,369,129). Pentane-1,5-diol has been used as an adjuvant component in the transdermal administration of the antihypertensive drug prazosine (WO 93/03697) in combination with a sulfhydryl-containing compound and a fatty ester. U.S. Pat. No. 5,550,145 discloses an antimicrobial composition comprising a monoglyceride and 5% by weight of pentane-1,5-diol. U.S. Pat. No. 4,241,084 discloses an antibacterial and antifungal composition comprising a sulfonamide and an alkylene glycol containing from 5 to 8 carbon atoms and an alkylene glycol ester. WO 96/11572 discloses a antimicrobial composition comprising carboxylic acids of up to ten carbon atoms or their salts and C3-C10-diols. WO 93/20812 discloses an antimicrobial composition comprising a) monoglyceride of lauric acid, a monoglyceride of mono-myristic acid or their mixtures, an antibacterial substance and a diol with 3-6 carbon atoms. EP 0 884 045 A1 discloses a self-tanning skin composition comprising a self-tanning skin coloring agent, a polyethoxyalcohol, a polyol and, optionally, a pentanediol. WO 98/27960 discloses a viscous hydrogel composition for topical administration comprising a microbially active nitro-imidazole drug, pentylene glycol and a hydroxyalkyl cellulose gelling agent and water, buffered to a physiologically acceptable pH. U.S. Pat. No. 5,879,690 discloses a composition for treatment of sagging subcutaneous muscle comprising an agent exhibiting or producing catecholamine activity and a carrier comprising skin penetration enhancer such as pentanediol. GB 2 280 111 A discloses clear gel antiperspirant compositions comprising an antiperspirant, pentanediol, a co-solvent of polyethylene glycol, water and/or glycerin, a buffering agent and a gelling agent.
Propylene glycol is a hygroscopic liquid widely used as a carrier in topical preparations. It is very hygroscopic and considered generally non-toxic (exception: ototoxicity) in contrast to ethylene glycol and hexylene-1,6-glycol (for a review, see: Goldsmith, L A. Propylene glycol. Int J Dermat 1978; 17:703-705).